The research proposed in this application is based upon the observation that the small intestinal mucosa of puppies suckled by their mothers increased in mass by approximately 75 percent over the first 24 hours of life whereas the the intestinal mucosa of similar animals fed artificially did not increase in mass. Initial studies will confirm this observation which suggests that canine colostrum contains a factor(s) which specifically stimulates growth of small intestinal mucosa. These studies will also determine the duration of the effect and if such an effect is exerted by mature canine milk. In addition, the nature and mechanism of the induced mucosal growth will be determined. Subsequent studies will determine if canine colostrum produces a similar trophic effect on the small intestinal mucosa of more mature animals and if the type of feeding prior to exposure to colostrum is an important determinant. The functional significance of the marked mucosal growth both with respect to nutrient transport by everted gut sacs and nutrient absorption from perfused intestinal segments will also be determined. In the same animals, non-invasive techniques of assessing small intestinal function (breath analyses following administration of labelled nutrients to evaluate nutrient absorption and sloughed DNA content of the intestinal perfusate to evaluate mucosal cell turnover) will be evaluated with respect to their efficacy in determining if human colostrum exerts a similar effect on the intestine of the human infant. Finally, the physicochemical nature of the trophic factor(s) will be investigated by determining if heating, freezing, dialysis or fat extraction abolishes the tropic effect. Organ culture will be used to compare the characteristics of growth induced by the colostrum factor with those induced by the polypeptide epidermal growth factor which is present in the milk of several animal species, including man. The entire project will provide valuable preliminary information concerning the feasibility of proceeding both to studies in the human and to actual isolation and characterization of the factor.